Device for producing hot water

ABSTRACT

The invention concerns a device for producing hot water comprising at least one burner ( 13 ) arranged to produce rapid combustion inside the combustion chamber. The combustion chamber consists of a sealed container ( 14 ) delimiting an internal volume separated from the water so as to allow dry combustion. Said container ( 14 ) is immersed in a water section ( 12 ) and it is extended by at least one smoke gas diffuser ( 15 ) diffusing the smoke gases above the water section within a mass of water showered by spraying means ( 10 ). A layer of nodules ( 11 ) can be interposed on the path of the smoke gases and the sprayed water so as to increase the thermal exchange generated, by direct contact between the smoke gases and the water spray, and by conduction between container ( 14 ) and water section ( 12 ). The invention enables to achieve excellent thermal efficiency levels while producing smoke gases with a reduced CO ratio.

FIELD OF THE INVENTION

The invention concerns a new device for producing hot water of the typecomprising a burner, in particular a gas burner, sustaining rapidcombustion in a combustion chamber.

BACKGROUND OF THE INVENTION

Conventional devices for producing hot water comprise a (generallytubular) exchanger wherein the water to be heated circulates in order totransfer calories through an exchange wall. The main drawback of theseexchange circuit devices lies in the poor heat transfer efficiencylevel.

A new type of device for producing hot water, referred to as directcontact device, has appeared in the past ten years, wherein the water tobe heated is sprayed and flows through the combustion chamber so thatthe exchange occurs directly without any interposed exchange wall; thistype of direct contact device is characterized in that the combustionchamber is wide open so as to allow direct contact between the flame andthe sprayed water. In this new type of device, a layer of transfernodules is most often arranged on the path of the smoke gases in orderto ensure more complete heat transfer. An excellent transfer efficiencyis thus obtained, that can be illustrated by the outlet temperature ofthe smoke gases which exceeds the temperature of the hot water obtainedby a few degrees only (of the order of 5 to 10° C.). External hot gasesare sometimes recovered and used as an additional heat input.

These direct contact devices are described in particular in thefollowing patents U.S. Pat. No. 4,275,708, U.S. Pat. No. 4,574,775, U.S.Pat. No. 5,293,861, EP-0,082,139. It can be noted that this recent hotwater production technique by direct contact had already been proposedin a very ancient U.S. patent (U.S. Pat. No. 884,223 delivered on Apr.7, 1908) which describes a gas ramp C arranged at the base of an opencombustion chamber E above which the water to be heated trickles.

Direct contact devices such as those described for example in patentsGB-2,129,916 and EP-0,387,983 allow to reach remarkable transferefficiency levels but they have several drawbacks. The most serious one,which considerably limits the development thereof, lies in the very highcarbon monoxide ratio observed in the smoke gases produced by this typeof device. This ratio, generally of the order of 500 to 700 ppm,remains, in the best case, above 150 to 200 ppm, which exceeds theratios authorized by most standards (housing: ratio below 100 ppm inFrance). Another drawback of these devices comes from the very hightemperature of the walls delimiting the combustion chamber (temperatureof the order of 800° to 900° close to that of the flame): these walls,situated in an air/sprayed water/steam atmosphere, undergo greatcorrosion stresses; they can be equipped with cooling circuits, but thisconsiderably increases the complexity and the cost of the device.

SUMMARY OF THE INVENTION

The present invention proposes a new device for producing hot water thatallows to reach the transfer efficiency levels of direct contact deviceswithout presenting the drawbacks thereof.

The main objective of the invention is to reduce the CO ratio of thegases discharged by direct contact devices to values equal or similar tothose of the gases discharged by conventional exchange circuit devices;ratios of the order of 20 to 40 ppm are obtained according to theinvention. These ratios can be obtained essentially for the followingreasons:

in the first place, in the device according to the invention, thecombustion obtained is a dry combustion carried out in a dry atmospherein the hearth-container,

furthermore, this combustion is a complete combustion.

Dry combustion is obtained in the device of the invention by designingand by arranging the smoke gas diffuser as defined in claim 1, so as tostrictly prevent any water inflow and any steam entry in thehearth-container. The water and the steam are forced back in thevicinity of the discharge ports of the diffuser by suitable overpressureof the diffuser and of the hearth-container. Furthermore, the positionof the diffuser and of its ports creates, in the vicinity of said ports,an air-lift type network that eliminates the internal secondarycirculations that tend to form at the gas outlet (a phenomenon referredto as slipstream), these secondary circulations producing an effect ofsuction of the damp atmosphere of the enclosure towards the combustionchamber.

Complete combustion is obtained in the device of the invention bycollecting the smoke gases at the end of the hearth-container situatedon the opposite side from the burner. These gases have thus stayed longenough in the hearth-container for the combustion to be complete.Furthermore, the upstream portion of the diffuser connecting thehearth-container to the diffusion portion extends this residence timeand allows in some cases (propane gas burner notably) to complete thecombustion before discharge of the smoke gases in the enclosure.

Another objective of the invention is to eliminate the drawbacks ofdirect contact devices due to the high-temperature corrosive atmosphereto which the walls of the combustion chambers are subjected in this typeof device.

The device for producing hot water according to the invention thereforecomprises an enclosure provided, in the upper part thereof, with smokegas discharge means, a combustion chamber consisting of at least onesealed contained referred to as hearth-container, extending along asubstantially horizontal axis and arranged in a water section situatedin the lower part of the enclosure, a burner associated with eachhearth-container and arranged at one end thereof to produce rapidcombustion extending along the horizontal axis of said hearth-containerover the length thereof, water spraying means, associated with coldwater delivery means and arranged so as to shower water in the upperpart of the enclosure, hot water extraction means situated in the lowerpart of the enclosure, said device being characterized in that:

each hearth-container is extended, at its end situated on the oppositeside from the burner, by a smoke gas diffuser comprising an upstreamportion connected to said end situated on the opposite side from theburner and a diffusion portion extending in the enclosure above thehearth-container according to a substantially horizontal axis,

the diffusion portion of the diffuser comprises smoke gas dischargeports provided in the lower half of the section of said portion so as toallow to establish an overpressure inside the diffuser and thehearth-container and to prevent water and steam entry in order to obtaina dry complete combustion inside said hearth-container,

water level control means being associated with the water section toensure, in said section, such a water level H that thehearth-container(s) are immersed in the water of said section and thatthe diffusion portion of the smoke gas diffuser remains constantly abovesaid water level.

In the device of the invention, the smoke gases are brought into directcontact, at the diffuser outlet, with the water showered into theenclosure, but the combustion is carried out in a confined spaceseparated from the water and the steam. Heat transfer occurs, on the onehand, by direct contact between the water and the smoke gases, and onthe other hand by conduction through the walls of the hearth-containerto the water of the water section; said diffuser(s) can also form anexchange surface in their upstream part connected to thehearth-container(s). Experiments have shown that, under such conditions,it is possible to simultaneously obtain:

a remarkable transfer efficiency level, of the same order as that of theaforementioned direct contact devices,

a reduced CO ratio in the smoke gases, of the same order as that ofconventional exchange circuit devices (20 to 40 ppm).

Achieving such a CO ratio, much lower than that of known direct contactdevices, can be explained by the fact that, in the device of theinvention, the combustion that takes place is a dry combustion protectedfrom water and steam, whereas it is performed in the presence of waterand steam in known direct contact devices. Water is a combustioninhibitor, as it is well-known, and its presence leads to incompletecombustion producing carbon monoxide that is found in the smoke gases.It can be noted that, in some known devices, the flame is more or lessprotected from too direct a contact with the water (cap H in patent U.S.Pat. No. 884,223 or combustion chamber set back in FIG. 10 of patentU.S. Pat. No. 4,895,136), but the combustion is not protected fromsplashes of water and it is in any case carried out in a damp atmosphereand in the presence of steam. Said steam constitutes an inert gas thatdilutes the combustible and combustive gases and reduces the probabilityof encounter between the reactive molecules, so that its presencecontributes to making the combustion incomplete.

It can be underlined that, in the invention, the internal volume of thehearth-container(s) is under overpressure in relation to the enclosureof the device as the rapid combustion occurs in a confined space (closedspace connected to the diffuser but not wide open as it is the case inknown direct contact devices): the steam contained in the enclosure thusdoes not tend to enter the hearth-container(s).

Furthermore, in the device of the invention, the hearth-container(s) areimmersed in the water section provided at the bottom of the enclosure,so that their temperature remains low (of the order of 100 to 120° C.);the walls of the hearth-container(s) are not subjected to severecorrosion stresses because, on the one hand, of their moderatetemperature, and on the other hand of their environment (liquid water onthe external face and dry atmosphere on the internal face).

The hearth-container advantageously has a cylindrical general shape ofsubstantially horizontal axis, the upstream portion of the diffuser isascending and the diffusion portion extends in the enclosure parallel tothe axis of the hearth-container.

More precisely, the diffusion portion of the diffuser comprises, as adischarge port, at least one longitudinal slot in the lower halfthereof.

The device can comprise a single hearth-container associated with asingle burner and a single diffuser. It can also comprise a singlehearth-container associated with several burners and a single diffuseror several diffusers. The device can also comprise severalhearth-containers associated each with one or more burners and one ormore diffusers.

According to a preferred embodiment, each burner is a nozzle-mixing typeforced-air gas burner in which the air and the gas are fed separatelyinto the burner nozzle so that the flame develops in the combustionchamber; said burner is secured outside the enclosure, its nozzleopening onto the inlet of the hearth-container in order to develop acombustion along the horizontal axis thereof Such a burner increases theoverpressure inside the hearth-container and guarantees combustion in adry atmosphere protected from any steam trace.

The burner, the hearth-container and the diffuser preferably constitutean assembly consisting of a single piece, mounted removably in anorifice of the enclosure wall.

The water level control means associated with the water section are ofany well-known type. In particular, they can comprise solenoid valvesmounted, on the one hand, on the cold water supply means and, on theother hand, on the hot water extraction means, and a water pressuredetector arranged at the base of the water section for controlling saidsolenoid valves so as to adjust the supply and discharge rate in orderto have a suitable adjustment of the water level in said water section.

Furthermore, as it is known in the art, at least one layer of heattransfer nodules is advantageously interposed between the water sprayingmeans and the smoke gas diffuser(s). This or these layers of nodulesprovide an additional heat transfer downstream from the primarytransfers mentioned above (exchange by direct water droplets/smoke gascontact; exchange by water/hearth-container and possibly diffuserconduction). The smoke gases are thus discharged at a very lowtemperature (smoke gas/hot water difference similar to that of knowndirect contact devices), which allows to increase the transferefficiency even further.

If need be, the device for producing hot water according to theinvention can recover, in some applications, the heat of availableexternal fumes in order to reduce the consumption of combustible gas inthe burner.

The device according to the invention therefore comprises at least oneexternal fumes inlet opening into the enclosure, above water level H.

According to an embodiment of the invention, the device can comprise atleast two layers of heat transfer nodules, the external fumes inletopening into the enclosure between said layers.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be clear fromreading the description hereafter of three embodiments given by way ofnon limitative example, with reference to the accompanying drawingswherein:

FIG. 1 is a section along a vertical plane of a first embodiment,

FIG. 2 is a detailed section of one of the elements along a plane AA,

FIG. 3 is a diagram illustrating the water level control means,

FIG. 4 is a diagrammatic view showing a subassembly of the devicedismounted, and

FIG. 5 is a front view of this subassembly in the direction shown byarrow V,

FIG. 6 is a vertical section of a second embodiment,

FIGS. 7 and 8 are diagrammatic views of a third embodiment, with avertical section BB and a horizontal section along a plane CCrespectively.

DETAILED DESCRIPTION OF THE INVENTION

The device for producing hot water shown by way of example in FIG. 1comprises an enclosure 1 consisting of a heat-insulated tank, made up ofa cylindrical wall 2 of vertical axis closed, in the lower part thereof,by a bottom wall 3 and, in the upper part, by a wall 4 convergingupwards and topped by a fumes exhaust line 5.

The lower part of cylindrical wall 2 comprises an oval-shaped orifice onwhose circumference a ring 6 provided with a flange allowing setting andfastening of a burner/hearth-container/diffuser assembly consisting of asingle piece, bearing reference number 7 in FIGS. 1 and 2 and describedhereafter, is welded (an assembly consisting of a single piece isunderstood to be an assembly that can come in form of a single piece,the various elements of this assembly can of course be dismounted andseparated).

A cold water supply line 8 opens into the upper part of tank 1. Asolenoid valve 9 is mounted on this line so as to allow supply rateadjustment.

Supply line 8 is bent so as to open into the tank along the verticalaxis thereof in form of water spraying means 10 comprising a spraynozzle suited to shower the water over the whole section of the tank.

This water falls on a layer of nodules 11 of a well-known type,consisting for example of a plurality of stainless steel rings having alarge surface of contact. The function of this layer is to providecomplementary cooling of the gases resulting from the combustion andsizeable reheating of the water flowing therethrough.

The bottom of the tank forms a water section 12 whose level H iscontrolled by means detailed below.

Assembly 7 consisting of a single piece essentially comprises a burner13 arranged to produce a combustion in a hearth-container 14 connected,on the opposite side from the burner, to a diffuser 15 that receives thesmoke gases produced by the combustion.

This assembly 7 is provided with a front plate 7 a whose shape iscombined with that of flange ring 6 so as to allow the assembly to beremovably fastened to tank 1.

Burner 13 is a nozzle-mixing type forced-air gas burner; it is securedoutside tank 1 with its nozzle 13 a opening into the inlet ofhearth-container 14. The air and the combustible gas driven separatelyinto said hearth-container perform a rapid combustion in saidhearth-container of cylindrical general shape and substantiallyhorizontal axis; the flame develops along the axis of saidhearth-container over the length thereof.

Smoke gas diffuser 15 is connected by its ascending portion 15 a to theend 14 a of the hearth-container on the opposite side from the burner.This portion is continued, after a 90° bend, by a diffuser portion 15 bextending above hearth-container 14.

In the example shown, connecting portion 15 a is a very short section;if need be, it is possible to lengthen it so as to form a heat exchangewall immersed in the water section.

In the present embodiment, diffusion portion 15 b is cylindrical(detailed FIG. 2) and extends substantially horizontally in tank 1. Itcomprises at least one smoke gas discharge slot such as 16 opening ontothe lower half of the section of said portion 15 b. In the exampleshown, two longitudinal slots extending along the portion are providedat an angle of 45° downwards in relation to the vertical mid-plane ofthe section. Of course, other types of opening can be provided, if needbe, on the lower half of said section in order to prevent any waterinflow in the diffuser. Protective lips can possibly be provided alongthe openings to increase the watertightness of the diffuser evenfurther. These layouts, associated with the overpressure produced by thecombustion and by the forced-air burner, provide in the hearth-containera dry atmosphere free of water and steam resulting from the ambience oftank 1.

In the lower part of water section 12, a main extraction line 17provided with a pump 18 and a solenoid valve 19 provides normaldischarge of the hot water during operation.

A secondary extraction line 20, provided with a solenoid valve 21normally closed, is provided in parallel with the main line in order toallow, if need be, additional water discharge through opening ofsolenoid valve 21.

The main and secondary hot water extraction is controlled in connectionwith the cold water supply by conventional control means suited toadjust the water level H of section 12 to an intermediate level betweenhearth-container 14 and diffuser 15, so that said hearth-container 14 isalways totally immersed in the water of section 12 and that diffusionportion 15 b always remains out of the water.

These control means comprise in this example, as shown in the figuresand notably in FIG. 3, a water pressure detector 22 mounted at the baseof the water section to deliver a signal representative of the waterpressure and therefore of the water level of section 12, a programmablecontroller 23 receiving this signal and programmed to actuate solenoidvalves 9, 19 and 21. During normal operation, the controller adjusts thesupply rate through solenoid valve 19 so that these flow rates conditiona water level H meeting the conditions defined above; in the steadystate, these flow rates are equal, control being performed by suitableflow rate adjustments. If need be, solenoid valve 21 allows to performan additional extraction in order to prevent a rise in the water level.

Furthermore, the device shown in the example is equipped with a safetysystem 24 that stops operation (cold water supply stop, burner stop) incase of lack of water, if the level of section 12 falls below apredetermined threshold. Accidental overheating of the walls ofhearth-container 14 is thus prevented. System 24 conventionallycomprises a capacitive detector 25 mounted on a by-pass line 26, adetector that controls stopping of burner 13 and closing of solenoidvalve 9 in the absence of water at the level thereof.

The device according to the invention produces hot water by combiningthe following main advantages:

a very high calorific output resulting from the complete nature of thecombustion and remarkable heat transfer levels by conduction and directcontact (hearth-container wall/water, smoke gas/water droplets, smokegas/water stream),

a reduced CO ratio in the smoke gases as a result of the complete natureof the combustion in a dry atmosphere,

low temperatures of the walls and notably of the walls of thehearth-container, which are the most exposed ones.

FIG. 6 illustrates another embodiment which differs from the first onein that it comprises two layers of nodules 27 and 28 situated on thepath of the smoke gases above the diffuser.

These two layers are separated by a volume through which the watershowers down. In this example, an external fumes inlet 29 opens intothis volume between nodule layers 27 and 28 in order to recover heatfrom available fumes coming from another plant.

Without departing from the scope of the invention, one or more externalfumes inlets can open onto one or more levels above water level H. Thelocation of these branch connections will be selected according to thetemperature level of the fumes and to the temperature gradient in theplant.

FIGS. 7 and 8 illustrate another embodiment wherein two burners 30 and31 of the same type as burner 13 are provided. If need be, it ispossible to provide a greater number of burners so as to reduce thepower of each one for a plant having a given global power. In theexample shown, each burner is associated with a hearth-container 32, 33and with a diffuser 34, 35 placed above the correspondinghearth-container. Furthermore, the assembly consisting of burners 30,31, hearth-containers 32, 33 and diffusers 34, 35 is made of a singlepiece and fastened as previously by means of a front wall 36 to thecylindrical wall of the tank.

What is claimed is:
 1. A device for producing hot water, allowing toproduce heat transfers by direct contact, with discharge of smoke gaseswith a reduced CO ratio, this device comprising an enclosure (1)provided, in the upper part thereof, with smoke gas discharge means (5),a combustion chamber consisting of at least one sealed containerreferred to as hearth-container (14), extending along a substantiallyhorizontal axis and arranged in a water section (12) situated in thelower part of the enclosure, a burner (13) associated with eachhearth-containing and arranged at one end thereof to produce a rapidcombustion developing along the horizontal axis of said hearth-containerover the length thereof, water spraying means (10) associated with coldwater supply means (8) and arranged to shower water in the upper part ofthe enclosure, hot water extraction means (17-19) arranged in the lowerpart of the enclosure, said device being characterized in that: eachhearth-container is extended, at its end (14 a) on the opposite sidefrom the burner, by a smoke gas diffuser (15) comprising an upstreamportion (15 a) connected to said end on the opposite side from theburner and a diffusion portion (15 b) extending in enclosure (1) abovehearth-container (14) along a substantially horizontal axis, diffusionportion (15 b) of the diffuser comprises smoke gas discharge ports (16)provided in the lower half of the section of said portion (15 b) so asto allow to establish an overpressure inside the diffuser and thehearth-container and to prevent any water and steam entry in order toobtain a dry complete combustion inside said hearth-container, waterlevel control means (9, 19, 21, 22 and 23) being associated with watersection (12) in order to provide, in said section, such a water level Hthat the hearth-container(s) are immersed in the water of said sectionand that diffusion portion (15 b) of the smoke gas diffuser remainsconstantly above said water level, wherein the control means comprisesolenoid valves (9, 19, 21) mounted, on the one hand, on cold watersupply means (8) and, on the other hand, on hot water extraction means(17, 20), and a water pressure detector (22) arranged at the base ofwater section (12) for controlling said solenoid valves in order toadjust the supply and extraction rates.
 2. A device for producing hotwater as claimed in claim 1, characterized in that hearth-container (14)has a cylindrical general shape of substantially horizontal axis,upstream portion (15 a) of the diffuser is ascending and diffusionportion (15 b) extends in enclosure (1) parallel to the axis ofhearth-container (14).
 3. A device for producing hot water as claimed inclaim 2, characterized in that diffusion portion (15 b) of the diffusercomprises as a discharge port at least one longitudinal slot (16) in thelower half thereof.
 4. A device for producing hot water as claimed inclaim 1, characterized in that each burner (13) is a nozzle-mixing typeforced-air gas burner wherein the air and the gas are driven separatelyto the burner nozzle so that the flame develops in the combustionchamber, said burner being secured outside enclosure (1) with the nozzleopening into the inlet of hearth-container (14) to develop a combustionalong the horizontal axis thereof.
 5. A device as claimed in claim 4,wherein burner (13), hearth-container (14) and diffuser (15) form anassembly consisting of a single piece, mounted removably in an orificeof the wall of enclosure (1).
 6. A device for producing hot water,allowing to produce heat transfers by direct contact, with discharge ofsmoke gases with a reduced CO ratio, this device comprising an enclosure(1) provided, in the upper part thereof, with smoke gas discharge means(5), a combustion chamber consisting of at least one sealed containerreferred to as hearth-container (14), extending along a substantiallyhorizontal axis and arranged in a water section (12) situated in thelower part of the enclosure, a burner (13) associated with eachhearth-containing and arranged at one end thereof to produce a rapidcombustion developing along the horizontal axis of said hearth-containerover the length thereof, water spraying means (10) associated with coldwater supply means (8) and arranged to shower water in the upper part ofthe enclosure, hot water extraction means (17-19) arranged in the lowerpart of the enclosure, said device being characterized in that: eachhearth-container is extended, at its end (14 a) on the opposite sidefrom the burner, by a smoke gas diffuser (15) comprising an upstreamportion (15 a) connected to said end on the opposite side from theburner and a diffusion portion (15 b) extending in enclosure (1) abovehearth-container (14) along a substantially horizontal axis, diffusionportion (15 b) of the diffuser comprises smoke gas discharge ports (16)provided in the lower half of the section of said portion (15 b) so asto allow to establish an overpressure inside the diffuser and thehearth-container and to prevent any water and steam entry in order toobtain a dry complete combustion inside said hearth-container, waterlevel control means (9, 19, 21, 22 and 23) being associated with watersection (12) in order to provide, in said section, such a water level Hthat the hearth-container(s) are immersed in the water of said sectionand that diffusion portion (15 b) of the smoke gas diffuser remainsconstantly above said water level, wherein at least one layer (11) ofthe heat transfer nodules is interposed between water spraying means(10) and smoke gas diffuser (15), and further comprising at least twolayers (27, 28) of heat transfer nodules and an external fumes inlet(29) opening into enclosure (1) between said layers.
 7. A device forproducing hot water, allowing to produce heat transfers by directcontact, with discharge of smoke gases with a reduced CO ratio, thisdevice comprising an enclosure (1) provided, in the upper part thereof,with smoke gas discharge means (5), a combustion chamber consisting ofat least one sealed container referred to as hearth-container (14),extending along a substantially horizontal axis and arranged in a watersection (12) situated in the lower part of the enclosure, a burner (13)associated with each hearth-containing and arranged at one end thereofto produce a rapid combustion developing along the horizontal axis ofsaid hearth-container over the length thereof, water spraying means (10)associated with cold water supply means (8) and arranged to shower waterin the upper part of the enclosure, hot water extraction means (17-19)arranged in the lower part of the enclosure, said device beingcharacterized in that: each hearth-container is extended, at its end (14a) on the opposite side from the burner, by a smoke gas diffuser (15)comprising an upstream portion (15 a) connected to said end on theopposite side from the burner and a diffusion portion (15 b) extendingin enclosure (1) above hearth-container (14) along a substantiallyhorizontal axis, diffusion portion (15 b) of the diffuser comprisessmoke gas discharge ports (16) provided in the lower half of the sectionof said portion (15 b) so as to allow to establish an overpressureinside the diffuser and the hearth-container and to prevent any waterand steam entry in order to obtain a dry complete combustion inside saidhearth-container, water level control means (9, 19, 21, 22 and 23) beingassociated with water section (12) in order to provide, in said section,such a water level H that the hearth-container(s) are immersed in thewater of said section and that diffusion portion (15 b) of the smoke gasdiffuser remains constantly above said water level, and furthercomprising at least one external fumes inlet opening into enclosure (1)above water level H.